By Dr. Peter Dahlberg, MD, PhD

October is breast cancer awareness month, which can take on different meanings from committing to helping a friend or family member through the treatment process, supporting local fund-raising efforts, or just remembering to schedule a mammogram. For our purposes today, let’s take a deep dive into risk factors for developing breast cancer, how to manage those risks, and maybe even how to modify them. Lifetime risks that women in the US will develop a breast cancer are 12%, or about 1 in 8, but risk can vary from 10% to nearly 80% in those who have inherited a mutated gene that makes it more likely for them to develop the disease.

A positive family history is one of the most familiar risk factors for developing breast cancer. Some patients that I talk to have a striking history of relatives who have had breast cancer, many at an early stage of life. Some of those patients believe that it is inevitable they will also be affected during their lifetime. Two mutated genes, BRCA1 and BRCA2, are responsible for the majority of “inherited” breast cancer cases. Most of these variants can be identified by a simple test, and there are several criteria that have been established to decide who ought to be tested. A family history of breast cancer, even in the absence of these mutated genes, also increases the risk of a family member developing breast cancer.

Reproductive history will modify a women’s risk for developing breast cancer. Most, but not all, breast cancers depend on the presence of the “female” hormones estrogen and progesterone for their growth. Exposure to these hormones’ changes throughout life, during pregnancy, and with post-partum breast feeding. At the extremes, a woman who begins to menstruate at a later age, has several children beginning when she is younger, breast feeds them for longer periods of time, and who goes through menopause at an early age will have a reduced risk of breast cancer as compared to one who menstruates early, goes through menopause later, and bears no children.

There are a few more risk factors that are more difficult to modify, age being the foremost. As with most tumors, breast cancer is a disease of aging. A prior history of breast cancer and even a history of a breast biopsy that shows “atypical” cells but is not interpreted as being a cancer can change an individual’s lifetime risk substantially. Breast density seen on a mammogram has also been noted to be a risk factor and is probably a reflection of estrogen exposure as is extra body mass, which affects estrogen metabolism. Hormone replacement therapy for treatment of menopausal symptoms as well as taking oral contraceptives are complex topics as they relate to breast cancer risk, but most current preparations are designed to minimize any addition to a women’s baseline risk.

So, how to make sense of all this? When you come to WWH for a mammogram, we ask you several questions that are designed to identify patients that might be at high risk for developing breast cancer (defined as greater than 20% over the lifetime). The next step in the process is to more precisely define exactly what a person’s lifetime risk is based on their individual data. For those whom the model predicts this to be greater than 20%, we discuss the pros and cons of high-risk screening which uses MRI testing in addition to yearly mammograms to identify any breast changes at an early stage. For very high-risk patients (greater than 35-40% lifetime), it might also be reasonable to consider a risk reduction strategy using medications that block some of the effects of estrogen. These drugs are used to treat women with breast cancer, typically for 5 years, but they have also been shown to reduce lifetime cancer risk by about half (50%) in high-risk individuals who do not already have breast cancer.

Take a while this month to increase your awareness about breast cancer. Stay active, work on lifestyle changes if you carry more weight than you would like to, schedule you yearly mammogram starting at age 40 (younger if you have relatives that were diagnosed with breast cancer at an early age), ask you primary care provider how to do a good breast self-exam, contact the American Cancer Society to participate in local events or volunteer to help a patient going through the challenging process of breast cancer treatment.

If you would like to make an appointment with a WWH primary care provider to discuss your risk factors, or schedule a mammogram please call 715-684-1111. Western Wisconsin Health-Building a healthier tomorrow, together.